For patients and other persons restricted to bed for extended periods of time, there arises the possibility of decubitus ulcers forming. Decubitus ulcers (also referred to as bed sores, pressure sores or pressure ulcers) are formed due to an interruption of blood flow in the capillaries below skin tissue due to pressure against the skin.
The highest risk areas for such ulcers to form are those areas where there exists a bony prominence which tends to shut down capillaries sandwiched between the bony prominence and the underlying support surface. When considering the redistribution of body weight and the formation of decubitus ulcers, the trochanter (hip) and the heels are the body sites of greatest concern since these two areas are most frequently involved in decubitus ulcer formations.
Blood flows through the capillaries at approximately 32 millimeters of mercury pressure (mm Hg). This level can be somewhat lower for elderly individuals or individuals with poor health or nutritional deficiencies. Thus, for the most part, once an external pressure exceeds 32 mm Hg, capillary occlusion occurs and the capillaries no longer supply oxygen and nutrition to the skin. Therefore, Tissue Trauma sets in with the resultant tissue decay and ulcer formation. Movement of the individual into different positions helps in restoring blood circulation into the effected areas. Such movement is, however, not always possible or, in some instances, neglected.
Various devices are relied upon by medical personnel and the like in attempting to avoid the problem of decubitus ulcers in bedridden individuals. For instance, air overlays and mattresses (static and dynamic), water overlays and mattresses, gel-like overlays, specialty care beds and foam overlays have been introduced in an attempt to avoid the problem of decubitus ulcers.
The prior art foam overlays, although generally cheaper than specialty beds and less complicated than some of the water mattresses and overlays, suffer from many drawbacks including:
(1) insufficient pressure reduction, especially in the hip and heel area;
(2) poor body/foam conformance which can lead to poor weight distribution and the development of high pressure points;
(3) discomfort due to high density foam or easily "bottomed out" pads;
(4) the placement of the person too high above the underlying mattress so as to decrease the safety factor; and
(5) high heat retention within the surface of the foam overlay.